Have you ever thought—really thought—about kissing? We take our mouths, which are generally used for eating and talking, and put them up against the mouths of others, and then move our lips and tongues around for awhile while keeping our eyes closed. Sometimes, when we're teenagers, we do it for hours and hours. And this dangerous germ spreading behavior is tied in somehow to romance or feelings of affection. Kissing is totally weird. A new book called The Science of Kissing aims to shed some light on your probably-pot-inspired questions about the reasons we tend to get turned on when we smush our faces together and make spit sounds.

According to author Sheril Kirshenbaum, kissing is not only a great way to get mono during your freshman year of college and miss a ton of parties, it's also an important way to assess physical compatibility with a partner prior to sex.

Kissing also provides "the chemical basis for falling in love," according to Kirshenbaum. When we kiss each other, our brains make an unconscious assessment of the hormonal components of the other person and decide whether or not it might be fun to take things further. A good kiss means a good match. Think makeout bingo.

On an anecdotal level, this isn't always the case; I've had brilliant makeout sessions with people who turned out to be about as much fun as a boner in church, and first kisses with people I've dated for long periods of time haven't all been stellar. Still, the notion of kissing being a way to assess actual chemistry is interesting, as I know more than one woman who knew that a breakup was imminent when her partner started to taste "off" to her or she began feeling un-turned on by the way his spit smelled.

According to the book, men view kissing as a means to an end (the end being "penis touching activity") and women tend to enjoy the act itself, and thus kissing exists for women moreso than it does for men. Kirshenbaum postulates that this may be because women can only have a limited number of offspring, we need to for be more selective in who we bone, and the act of kissing gives us more information that we need to determine whether or not our partner would make a good father (or, at the very least, suitable cunnilingus partner).

No word yet on when humans will incorporate knowledge of the existence of The Pill into what drives our mating behaviors, or if it's just more convenient for Science to repeat the "women love monogamy because of babies; men love whoring around" trope.